1class Material:
  2    def __init__(self, mass, density):
  3        self.mass = mass
  4        self.density = density
  5        self.usable = True
  6
  7    @property
  8    def volume(self):
  9        return float(self.mass) / self.density
 10
 11    def use(self):
 12        if not self.usable:
 13            raise AssertionError("Material isn't usable.")
 14        self.usable = False
 15
 16
 17class Concrete(Material):
 18    def __init__(self, mass):
 19        super().__init__(mass, density=2500)
 20
 21
 22class Brick(Material):
 23    def __init__(self, mass):
 24        super().__init__(mass, density=2000)
 25
 26
 27class Stone(Material):
 28    def __init__(self, mass):
 29        super().__init__(mass, density=1600)
 30
 31
 32class Wood(Material):
 33    def __init__(self, mass):
 34        super().__init__(mass, density=600)
 35
 36
 37class Steel(Material):
 38    def __init__(self, mass):
 39        super().__init__(mass, density=7700)
 40
 41
 42class Factory:
 43    _fusions = {}
 44    __class_instances = []
 45
 46    def __init__(self):
 47        self.__class_instances.append(self)
 48        self._materials = []
 49
 50    def __del__(self):
 51        self.__class_instances.remove(self)
 52
 53    @property
 54    def volume(self):
 55        return sum(material.volume for material in self._materials if material.usable)
 56
 57    def can_build(self, volume):
 58        return self.volume >= volume
 59
 60    @classmethod
 61    def can_build_together(cls, volume):
 62        return sum(
 63            material.volume
 64            for factory in cls.__class_instances
 65            for material in factory._materials
 66            if material.usable
 67        ) >= volume
 68
 69    def __call__(self, *args, **kwargs):
 70        if args and kwargs:
 71            raise ValueError("Only positional or keyword arguments are allowed, not both.")
 72
 73        if not args and not kwargs:
 74            raise ValueError("Factory can't be called without arguments.")
 75        
 76        if kwargs:
 77            materials = []
 78            for name, mass in kwargs.items():
 79                material_class = globals().get(name)
 80                if not material_class:
 81                    material_class = self._fusions.get(name,None)
 82                    if not material_class or not issubclass(material_class, Material):
 83                        raise ValueError("Invalid material.")
 84                material = material_class(mass)
 85                materials.append(material)
 86                self._materials.append(material)
 87            return tuple(materials)
 88
 89        if args:
 90            new_args = []
 91            for material in args:
 92                if type(material).__name__.__contains__("_"):
 93                    # here we get the class name from the globals and use its init with the material mass
 94                    new_args += map(lambda name: globals()[name](material.mass), type(material).__name__.split("_"))
 95                else:
 96                    new_args.append(material)
 97
 98            class_name = "_".join(sorted(set(type(material).__name__ for material in new_args)))
 99            if class_name not in self._fusions:
100                density = sum(material.density for material in new_args) / len(new_args)
101
102                class Fusion(Material):
103                    def __init__(self, mass):
104                        super().__init__(mass, density=int(density))
105
106                Fusion.__name__ = class_name
107                self._fusions[class_name] = Fusion
108
109            total_mass = sum(material.mass for material in new_args)
110            new_material = self._fusions[class_name](total_mass)
111            for material in args:
112                material.use()
113            self._materials.append(new_material)
114            return new_material